You can clone with
No one assigned
When opening a new file, the file's content appears a fraction of a second before the syntax highlighting is done.
Noticed this also. Most Relevant factors appear to be 1. the pure length of the file (Lag very noticeable when editing a 3000 line marked up text) and 2. density of the markup (e.g. more noticeable on .min.js files). .
SH should be much faster nowadays.